Virtual versus real design of a traffic light/voice controller

The traffic light/voice controller is a sequential machine to be analyzed and programmed through a multi-step process. Both the hands-on and the virtual environments are described. The design projects of the four teams of fourth year students who developed the device involved: analysis of existing sequential machines in traffic light controllers, timing and synchronization, role and introduction of LEDs and of the push buttons for pedestrian walk requests and visual signals and various regimes of operation and flashing lights/voice synthesis sequence. The light system comprises a programmable ALTERA logic unit with a wired up set of LEDs and other electronic components. A low cost complex programmable logic device (CPLD) by ALTERA is used in the voice synthesis part of the traffic controller interface. The novelty of this digital design project is given by the systematic procedure set for the analysis of the controller operation and of the various circuits and digital elements involved. A CVI-based (computer visualization interface) simulation accompanies the real-time operation of the traffic light controller and time simulations of electric signals (shift registers for machine states) are also part of this teaching/learning tool. The students and other users can perform a virtual (remote) operation of the lights/voice sequence, test the electronic components and the programmable unit and check their results with the CVI simulation.